Numerous tools and techniques have been developed for repair of damaged plate glass surfaces, especially those made of laminated "safety" glass such as is used in automotive windshields. The cost benefit of repairing small cracks rather than replacing an entire windshield to restore the visual integrity of the windshield is substantial. Common windshield damage, such as that caused by impact from small rocks or gravel, may be in small chips, cracks, "bullseyes" and "stars." While such damage may be confined to a small area, and may or may not significantly affect the transparency or optical clarity of the windshield, repair of such damage may be readily accomplished and may prevent further damage due to cracks which may spread from the damaged area as a result of stress created by, for example, temperature induced expansion and contraction of the glass or mechanical vibration.
The common methods of repair involve variations of the basic steps of (1) providing an airtight seal around the broken area (2) drawing a vacuum to remove air from the broken area and (3) introducing a suitable resin into the broken area under either ambient atmospheric pressure or under a positive pressure.
In such glass repair, the success of the repair, both structurally and visually, may be primarily dependent on the extent to which the damaged area is filled with repair resin without leaving voids or air bubbles within the repaired area. It has been recognized in the prior art that alternating cycles of vacuum and pressure may be desirable in order to maximize the removal of air from within the broken area and of air which may be entrained or dissolved in the repair resin.
U.S. Pat. No. 3,765,975 to Hollingsworth describes a method involving the application of both vacuum and positive pressures to repair resin at a repair area. The pressure changes are created by manual operation of a syringe plunger.
U.S. Pat. No. 3,993,520 to Werner, disclosing a device for repairing glass, describes manually adjustable screw actuators to select the application of alternating vacuum and pressure cycles to accomplish the removal of entrained air from the broken area.
U.S. Pat. No. 4,047,863 to McCluskey shows a continuously operable electrical vacuum pump connected by a line to resin in a glass crack repair chamber and having finger controlled means for controlling the vacuum by admission of air to the line. It further describes the use of a manually operated mechanical piston to apply pressure to the resin.
U.S. Pat. No. 4,280,861 to Schwartz discloses a device employing a vacuum pump to hold an enclosure cup in place to enable insertion of a syringe with resin for repairing glass. Schwartz also shows a system of manually selectable shut-off valves which can be manipulated to control a remote compressor pump or a remote vacuum pump which may be used to apply pressure or vacuum to a pool of resin material. Gauges inform the operator as to the amount of pressure or vacuum being applied during the repair process being observed.
U.S. Pat. No. 4,597,727 to Birkhauser shows a glass repair method with an arrangement of a pressure gauge and manually adjustable valves to selectively switch a manually operated pump from creating in successively increasing steps the degree of vacuum at the repair material to a final step of applying positive pressure to the repair material.
U.S. Pat. No. 4,032,272 to Miller shows another break repair device using a vacuum pump whereby the device is held by vacuum over the break in the glass.
The prior art methods and systems have typically required the attention of and control by the technician through the time required to complete the repair process, i.e. reading gauges, recording times and manually adjusting valves. Such operator control has also often required a degree experience or skill by the operator. In contrast the present invention is intended to provide a system in which the device is essentially automated to allow unattended operation even by a relatively unskilled operator.